EIII doesn't boot anymore when 8 Mb memory upgrade kit is installed

[Liberty]

Hi there E-mu family,
I have an EIII bought in L.A. in 1989, Model 6081, Serial #0890671, and I recently had the original Internal 40 Mb Quantum HD replaced by an SCSI2SD 3.5" card, including a 50-pin SCSI to SD Card Adapter.
A 4 Go SD card was formatted with EMXP v311 and EIII OS 2.42 copied with HDD Raw Copy and it is now the Internal Drive the EIII boots from. It boots and works flawlessly, with the factory 4 Mb ram installed.

We then purchased the 8Mb memory upgrade kit 6084, featuring 8 x 1 Megabyte SIMM?s (1C356) + 2 IC, RAS PAL (IP376) and Address PAL (IP377), and installed it thoroughly according to the E-mu Systems Inc. memory expansion instructions manual, but unfortunately, the unit won?t boot anymore?
It starts loading from the SD card (SCSI #1) (or even the Floppy drive), but get stuck in the process and never completes the task. As soon as we re-install the old 4 Mb kit however, the unit boots and works without any problems.
 
Any suggestions ? Would anybody be aware of some incompatibility issues with Ram upgrade on certain EIII models ?
Could the problem be defectuous PAL376 and 377 circuits ? I was told that bad ram modules won?t prevent the EIII to boot.
Any idea of some tests to perform ?

Many thanks for your suggestions and advices.

[Stephencl]

Hello, which firmware version is your EIII? I think I remember that the original EIII firmware was incompatible with the 8mb upgrade kit.